Scanning-head printers typically maintain a print head within a movable carriage. A paper drive is used to deliver paper to a position next to the carriage. The carriage is repeatedly moved back and forth, or "scanned", across the surface of the paper, with the print head applying print to the paper. After each pass of the carriage across the surface of the paper, the paper drive advances the paper to present a new region, or line, of the paper to the print head.
Conventional scanning-head printers use multiple motors to accomplish the printing process, since there is an inherent incompatibility of moving parts with respect to both the direction and timing of the movement. For example, a first motor provides a periodic, linear motion to the paper drive components for paper advancement, while a separate second motor is used to provide a substantially continuous, reciprocating motion to the carriage, with the reciprocating motion of the carriage being perpendicular to the direction of paper advancement.
The use of multiple motors achieves a cooperation of components for operating the printer, but increases the size, mass, and cost of the printer. Each motor requires electrical controls and gears to insure that the carriage or paper is moved an appropriate distance. These motors, controls, and gears add to the size, the mass, and the cost of the printer. Additionally, the housing of the printer must be sufficiently large to accommodate the above-mentioned components. Furthermore, because power must be supplied to multiple motors and electrical controls, power consumption is also increased in multiple motor scanning-head printers.
The drawbacks associated with scanning-head printers are especially problematic in the field of portable scanning-head printers, which ideally are in as compact a form as possible in order to enhance mobility with the size, it is desired to minimize the mass or weight of a portable printer. Multiple motors, electrical controls and gears, however, increase the size and weight of the printer.
Additionally, portable printers often function using finite power sources, such as batteries. Therefore, it is further desired to keep the power consumption of the printer at a minimum. The use of multiple motors and electrical controls, however, tends to quickly deplete limited power supplies.
Therefore it is an object of the present invention to provide a scanning-head printer having a smaller size and a lighter weight, which operates using less power, and which achieves these results at a reduced manufacturing cost. It is a further object of the present invention to provide a scanning-head printer which is compatible for use in portable printer applications.